Memory access error despite allocating memory properly - c++

Question

struct SourceInfo {
const char *filename;
int line, col;
};
struct Node;
struct Lexer {
private:
FILE *File;
std::string Filename;
char* test;
int Line;
int Column;
static const int MAX_LINE_LENGTH = 1024;
public:
Lexer(FILE* in, const char* filename)
{
File = in;
test = new char[strlen(filename)+1];
strcpy(test, filename);
Filename = std::string(test);
Line = 0;
Column = 0;
}
~Lexer() {
}
Node *next() {
return nullptr;
}
Node *peek() {
return nullptr;
}
SourceInfo get_current_pos() {
SourceInfo info;
info.filename = Filename.c_str();
info.line = Line;
info.col = Column;
return info;
}
};
////////////////////////////////////////////////////////////////////////
// Lexer API functions
////////////////////////////////////////////////////////////////////////
struct Lexer *lexer_create(FILE *in, const char *filename) {
return new Lexer(in, filename);
}
void lexer_destroy(struct Lexer *lexer) {
delete lexer;
}
struct Node *lexer_next(struct Lexer *lexer) {
return lexer->next();
}
struct Node *lexer_peek(struct Lexer *lexer) {
return lexer->peek();
}
struct SourceInfo lexer_get_current_pos(struct Lexer *lexer) {
return lexer->get_current_pos();
}
/* The setup function creates the test fixture. */
TestObjs* setup();
/* The cleanup function cleans up the test fixture. */
void cleanup(TestObjs* objs);
//Test functions
void testCreate(TestObjs* objs);
void testGetCurrentPosAtBeginning(TestObjs* objs);
int main(int argc, char** argv) {
if (argc > 2) {
printf("Usage: %s [<test name>]\n", argv[0]);
return 1;
}
/*
* If a command line argument is passed, it's the name
* of the test to be executed.
*/
if (argc == 2) {
tctest_testname_to_execute = argv[1];
}
/*
* Install test execution hook.
* (Only test suites that need to do detailed monitoring or
* reporting of test execution will need to do this.)
*/
//tctest_on_test_executed = onTestExecuted;
/*
* Install completion hook.
* (Only test suites that need to do something special
* to report results really need to do this: TEST_FINI
* generates a reasonable human-readable summary of
* the executed tests.
*/
//tctest_on_complete = onComplete;
/* Prepare to run tests */
TEST_INIT();
/* Execute test functions */
TEST(testCreate);
TEST(testGetCurrentPosAtBeginning);
/*
* Report results: exits with nonzero exit code if
* any test failed
*/
TEST_FINI();
}
TestObjs* setup() {
TestObjs* objs = malloc(sizeof(TestObjs));
return objs;
}
void cleanup(TestObjs* objs) {
lexer_destroy(objs->lexer);
free(objs);
}
void testCreate(TestObjs* objs) {
const char *filename = "testFile.txt\0";
objs->filename = (char*) malloc(sizeof(char) * (strlen(filename) + 1));
strcpy(objs->filename, filename);
FILE* in = fopen(objs->filename, "r");
objs->lexer = lexer_create(in, objs->filename);
}
void testGetCurrentPosAtBeginning(TestObjs* objs) {
struct SourceInfo info = lexer_get_current_pos(objs->lexer);
ASSERT(info.line == 0);
ASSERT(info.col == 0);
ASSERT(strcmp(objs->filename, info.filename) == 0);
free(info.filename);
}
For some reason, I am getting a segmentation fault in testGetCurrentPosAtBeginning function. I do not why this error is occurring because I managed the memory properly. I looked through GDB and was puzzled as to why this error is occurring.
To me, it looks like memory is going out of scope at the constructor but I am not sure. The test functions are based off of TCTest, a test framework for C.

Answer 1

For some reason, I am getting a segmentation fault in
testGetCurrentPosAtBeginning function. I do not why this error is
occurring because I managed the memory properly.
It is occurring because you are not managing memory properly.
In particular, testGetCurrentPosAtBeginning() does this:
free(info.filename);
You must free only pointer values obtained from malloc() or another memory-allocation function, but if we trace the source of info.filename, it ultimately comes from
info.filename = Filename.c_str();
in method Lexer::get_current_pos(). This is not a string you should attempt to free.